const fp = require('lodash/fp')

const cars = [
  {
    name: 'Ferrari FF',
    horsepower: 660,
    dollar_value: 700000,
    in_stock: true
  },
  {
    name: 'Spyker C12 Zagato',
    horsepower: 650,
    dollar_value: 648000,
    in_stock: false
  },
  {
    name: 'Jaguar XKR-S',
    horsepower: 550,
    dollar_value: 132000,
    in_stock: false
  },
  {
    name: 'Audi R8',
    horsepower: 525,
    dollar_value: 114200,
    in_stock: false
  },
  {
    name: 'Aston Martin One-77',
    horsepower: 750,
    dollar_value: 1850000,
    in_stock: true
  },
  {
    name: 'Pagani Huayra',
    horsepower: 700,
    dollar_value: 1300000,
    in_stock: false
  }
]

// 练习1
// let isLastInStock = function (cars) {
//   let last_car = fp.last(cars)
//   return fp.prop('in_stock',last_car)
// }
let isLastInStock = fp.flowRight(fp.prop('in_stock'),fp.last)
console.log(isLastInStock(cars))

// 练习2
let firstName = fp.flowRight(fp.prop('name'),fp.first)
console.log(firstName(cars))

// 练习3
let _average = function (xs) {
  return fp.reduce(fp.add,0,xs) / xs.length
}
// let averageDollarValue = function (cars) {
//   let dollar_value = fp.map(function(car){
//     return car.dollar_value
//   },cars)
//   return _average(dollar_value)
// }
let averageDollarValue = fp.compose(_average,fp.map(car => car.dollar_value))
console.log(averageDollarValue(cars))

// 练习4
let _underscore = fp.replace(/\W+/g,'_')

let sanitizeNames = fp.flowRight(fp.map(_underscore),fp.map(car => car.name))

console.log(sanitizeNames(cars))